Related Clues:

• This invoice does not sound so low
• All the voices sound not so low
• No so low?
• Refrain from singing
• Madrigal syllables
• See 19
• Nanki-poo's sequel to spring flowers
• Sinatra label covered 'Expression of Joy'
• The Hallelujah girls?
• Either sing together or refrain
• Singing group - refrain
• Supporting singers and dancers
• Sing(ing) together
• Sound made when humming a song
• Pipe up in unison